1. Field of the Invention
The present invention relates to an optical disc medium and an apparatus and method for recording and reproducing data on and from the optical disc medium.
2. Description of the Related Art
In optical disc media, in which data is recorded by using minute optical spots, a ROM (Read Only Memory) medium was popularized on which a sequence of embossed data pits was previously formed. Subsequently, data recordable type optical discs such as CD-R (Compact Disc-Recordable) and DVD-R (Digital Versatile Disc-Recordable) have been widely used. Also, optical disc media such as so-called CD-RW (CD-ReWritable) and DVD-RW (DVD-ReWritable) are known in which data can be rewritten. Here, the optical disc medium on which data can be recorded by a user is referred to as a recordable type optical disc medium.
In the recordable type optical disc medium, a spiral groove track is formed on an optical disc substrate for tracking and a multi-layer record layer of organic materials is formed on it, for example. Data are recorded by focusing a high-power laser beam onto the record layer, to partially change the property of the record layer for forming record pits therein. The recorded data can be reproduced by a read-only disc drive apparatus, since such a medium has a same data format as a ROM medium having an embossed data pit sequence after a recording operation so that a same servo signal as from the ROM medium can be reproduced.
In the DVD-R medium, user data is converted in format to have additional data, e.g., data ID as an address and error correction code, and the converted user data is recorded as a sequence of continuous data on the optical disc medium. The format in which data are continuously recorded is same as that of a DVD-ROM medium.
However, if the format is completely the same as that of the DVD-ROM medium, the recording operation can be carried out only once. For this reason, so-called multi-session and multi-border recording methods are set to allow data to be recorded for several times. In this case, special data so-called border area data are recorded behind user data to contain record location data, and then new user data is recorded behind the border area data. Thus, a data reproducing apparatus reproduces the user data by using the record location data.
As shown in FIG. 3, a recordable optical disc medium 6 has a spiral record track 24. The record track 24 has concentrically a system area 22, a data area 23, and a read-out area (not shown) outward from the center.
The system area 22 is used to record system data necessary for recording and reproducing operations, such as disc data and an area for data recorded by a user. In this system area 22, there are an area for recording disc control data and an area for the test of a recording condition.
The read-out area is an area that indicates the end of the recording area of the disc. When the read-out area is detected, the end of the recording area on the optical disc medium is recognized.
The data area 23 is provided on the outer side of the system area 22 to record the user data.
FIG. 4 shows the data structure of the optical disc medium 6 in one dimension. As shown in FIG. 4, in the data structure on the optical disc medium 6 in the radial direction, the left side is on the side of a disc inner circumference, while the right side is on the side of a disc outer circumference. The system area 22 on the inner circumference side is an area where system control data necessary for optical disc apparatus to record and reproduce data, data indicating a record location of data on the optical disc medium 6, and the like are recorded. The system area 22 is mainly classified into three areas: a recording operation test area 26, a record control data area 27, and a user data lead-in area 28.
The user data lead-in area 28 is provided in an area closest to the data area 23. The system control data necessary for a read-only optical disc apparatus to reproduce data on a recordable optical disc medium on which data is already recorded is mainly recorded in the area.
In the record control data area 27 are mainly recorded data necessary for the optical disc recording apparatus to record the user data onto the data area 23, i.e., data indicating the next location for user data to be recorded in the data area 23 and usage status of the recording operation test area 26. The data in the area 27 is updated each time the data is recorded additionally in the data area 23. Accordingly, new data are recorded in the area 27 from the inner circumference side to the outer circumference side in a predetermined unit.
The recording operation test area 26 is an area used to carry out a trial recording operation for checking an optimal recording condition. The trial recording operation is carried out while altering the power and waveform of a laser beam, to optimize the recording condition into the data area 23. Area portions of the recording operation test area 26 may be used in an optional order, but the outer area is usually used first.
FIG. 6 is a flow chart showing a recording operation for recording user data on the optical disc medium. When the user data is recorded, a recording operation preparing process (S11) is first carried out. In the recording operation preparing process, a trial recording operation is carried out while altering writing power or waveform of a laser beam by using recording operation test area 26, and the optimal recording condition for recording the user data is determined. The optimal recording condition is set as a condition for recording the user data in the data area 23 (S11) After the setting of the recording condition, a user data recording process is carried out to record user data in the data area 23 (S12).
After the user data recording process is ended, a recording operation end process is carried out (S13). The recording operation end process is sometimes called a finalizing process, and is a process for allowing the user data to be reproduced by a read-only optical disc apparatus. In the recording operation end process, a continuous record pit sequence having a length is formed before or after the user data to allowing reliable access by the read-only optical disc apparatus, because the read-only optical disc apparatus can access stably only to an area where the record pits are formed continuously.
As shown in FIG. 5, after the recording operation end process, there are the area where the record pits are formed and the area where the record pits are not formed. There are a data recorded area 23a and a data free area 23b in the data area 23. When the recorded data quantity is smaller in the data area 23 or when the number of times of an additional recording operation is smaller, a record control data recorded area 27a and a control data free area 27b are present in the record control data area 27 and a recorded area 26a and a free area 26b are present in the recording operation test area 26.
Data necessary for the reproducing apparatus to reproduce the recorded data on the optical disc medium 6 is recorded in the user data lead-in area 28. The data quantity of the user data lead-in area 28 is not so large. However, the user data lead-in area 28 is also used as a guard area 30 for prevention of the tracking-out when the data area 23 is accessed. For this reason, the user data lead-in area 28 is required to have the width-of 100 μm or more in the radial direction. In the recording operation end process to an actual optical disc medium 6, the guard area is often formed additionally outside the recorded user data in the data area 23.
In the read-only optical disc apparatus, since a track error signal is generally detected from the record pits, it is not possible to access to the free area. Therefore, the user data lead-in area 28 and the data recorded area 23a in the data area 23 which form a sequence of record pits, are the reproducible area by any type of optical disc apparatus.
The system area 22 is an area essential for the optical disc apparatus to record and reproduce data, although the area is invisible to a user. Accordingly, the capacity of the optical disc medium recognized by the user is the capacity of data area. Because the optical disc medium is desired to have a capacity as large as possible, the system area is desired to be smaller.
However, as described above, it is difficult to reduce the system area, for ensuring the number of times of the addition recording operation and the stability of the read-only optical disc apparatus.
In conjunction with the above description, an optical disc is disclosed in Japanese Laid Open Patent Application (JP-P2000-48370A). The optical disc in this conventional example has a reproduction exclusive area where a plurality of reproduction exclusive tracks are formed and the rewritable area where a plurality of rewritable tracks are formed. Each of the plurality of reproduction exclusive tracks is divided into a plurality of first sectors, and a signal of a predetermined reproduction format is previously recorded to at least one of the plurality of first sectors. At least one of the plurality of first sectors has compatibility with a reproduction exclusive optical disc in which the signal of the predetermined reproduction format is previously recorded. Each of the plurality of rewritable tracks is divided into a plurality of second sectors. A signal of any of predetermined record formats which contains the predetermined reproduction format can be recorded in at least one of the plurality of second sectors. The reproduction exclusive area is arranged on the internal circumference side of the optical disc side and the rewritable area is arranged on the outer circumference side of the optical disc.
Also, an optical disc recording method is disclosed in Japanese Laid Open Patent Application (JP-P2003-249020A). In this conventional example, the last position data of the recorded data on an optical disc to which a recording operation cannot be carried out and data of an initial record possible capacity are detected. A data record possible capacity of a free area is determined from the last position data of the recorded data of the optical disc and the data of the initial record possible capacity, and data is recorded to the free area subsequent to the last position indicated by the last position data.
Also, an information recording method is disclosed in Japanese Laid Open Patent Application (JP-P2002-208139A). In this conventional example, a recording operation is carried out to keep a record linear density approximately constant while changing a record clock period according to the change of the record line speed, when mark data is recorded onto an optical disc medium which has a record layer by a laser beam with a light emission waveform determined based on a record pulse string. Also, when the recording operation is carried out using a record power calculated from an approximate equation to get the record power corresponding to the change of the record line speed, data recorded in an end portion of a recorded area as one of a plurality of record areas obtained by dividing an area of the optical disc medium in a radial direction is reproduced. The approximate equation is derived to which a correction of the record power is carried out such that an ideal signal characteristic is gotten from the signal characteristic gotten from the reproduction signal. The recording operation is carried out using the record power which is calculated from the approximate equation to each area.